The level of FOX-1 produced by yIs44 causes complete XO-specific lethality in otherwise wild-type strains. In yIs44 strains with the gfp::
xol-1 arrays, no GFP expression was detected and all the XO animals died. These results indicate that high doses of FOX-1 drastically reduce the levels of both the GFP::XOL-1 protein and the endogenous XOL-1 protein, revealing that FOX-1 acts through
xol-1.